1. Field of the Invention
The present invention relates to a method and apparatus for searching a rights object and a mapping method and mapping apparatus for the same, and more particularly, to a method and apparatus for searching a rights object and a mapping method and mapping apparatus for the same, in which a rights object ID and a content ID are mapped and managed to increase the efficiency of search for a rights object.
2. Description of the Related Art
Recently, digital rights management (hereinafter referred to as “DRM”) has been researched actively, and commercial services using DRM have already been implemented or will be implemented. DRM is a technical concept to protect digital content that can be readily copied and distributed without permission.
Although efforts have been made to protect digital content, conventional digital content protection has focused mainly on preventing unauthorized access to digital content. Specifically, only those people who have paid fees are permitted to access the digital content, and those who have not paid the charges are denied access to the digital content. However, the digital content can be readily copied, reused, processed and distributed to third parties due to the characteristics of the digital data.
Accordingly, when a person who has paid the fees accesses the digital content and intentionally distributes it to a third party, the third party can use the digital content without paying the fees, which has produced a number of problems. In order to solve these problems, in DRM, the digital content is encrypted and distributed, and a specified license called a rights object (RO) is needed to use the encrypted digital content.
However, a rights object stored in host devices can be readily transferred and copied on portable storage devices. Overcoming limitations of conventional storage devices such as hard disks and compact disks, portable storage devices such as XD cards and multimedia cards, which can easily be connected and disconnected from host devices such as mobile phones, computers and digital cameras, can carry out data control and computing functions in addition to data storage. Further, new portable storage devices having security functions for use with the above-described portable storage devices are being developed, in which copyrighted digital content can be protected by securing content during transmission and storage. Accordingly, it is possible to implement DRM between a portable storage device and a host device. That is, a rights object can be stored in the portable storage device, and the host device can regenerate encrypted digital content using the rights object stored in the portable storage device.
FIG. 1 is a conceptual diagram of a method of installing a conventional rights object.
A host device sends a rights object identifier (RID) to a portable storage device to store a rights object (S11). RID is usually included in the rights object and serves as a unique identifier for the rights object.
After receiving the RID, the portable storage device allocates a rights slot and sends a response to the host device (S13). The host device then transmits a rights object to the portable storage device (S15).
Thereafter, the portable storage device stores the rights object in the allocated rights slot with the RID serving as a search key (S17). Here, the RID is used as a unique identifier for allocating a memory space for the rights object. When the RID is used as a search key, a hash value having a specific length of 20 bytes or a value of a specific attached string is used as a search key.
Meanwhile, host devices can use a content identifier (CID) or RID to search for a corresponding rights object stored in a conventional portable storage device. CID is usually included in the rights object and serves as a unique identifier for content.
In the case of performing a search by using a rights object identifier, the host device searches a memory space corresponding to the rights object identifier to retrieve the rights object stored in the searched memory space.
In the case of performing a search by using a content identifier, the host device searches for content identifiers in all of the rights objects to retrieve the rights object corresponding to the content identifier.
Accordingly, when searching for a rights object by using a content identifier, content identifiers in the rights objects must be parsed and searched in a comparative manner. As a result, the cost of parsing increases and the search speed decreases. Further, there is a problem of regenerating content in real time due to the delayed response time.